Synthesis Of Bishydroxy Phosphoramidate And Its Application In Flame-retardant Finishing Of Cotton Fabrics

As a natural fiber with abundant reserves,cotton fiber is widely used in production and living fields such as household textile,clothing,automobile and other industries.Cotton fabrics have excellent biodegradability and moisture permeability,but the LOI of cotton fabrics is only about 18%,which suggests it is easy to burn.Every year,there are countless casualties and economic losses caused by the fire of cotton fabrics.Therefore,the flame retardant research of cotton fiber is significant.With the improvement of people's living standards,the requirements for formaldehyde emissions from textiles are getting stricter.The issue of formaldehyde release from textiles has become the focus of scientific research,and the development of formaldehyde-free flame retardants and treating methods is imperative.In this paper,a flame retardant DMHPA containing nitrogen and phosphorus was synthesized and the treating method was studied.A novel phophoramidate compound,Dimethyl-N,N'-bis(2-hydroxyethyl)phosphoramide(DMHPA)was synthesized using dimethyl phosphite and diethanolamine by Atherton-Todd reaction,and characterized by FTIR,NMR.ATR-FTIR and NMR results showed that the chemical characteristics of the synthesized product were consistent with the target,which suggested that DMHPA with high purity was synthesized successfully.Cotton fabrics were treated with different concentrations of DMHPA,FT-IR,SEM,EDS were used to characterize the chemical structure,surface morphology of the treated sample.To further investigate the flame retardant and thermal degradation of treated samples,limiting oxygen index(LOI),vertical flammability test(VFT),thermogravimetry(TG)and CCT were analyzed.The results of SEM,FTIR and EDS show that the flame retardant DMHPA was successfully treated onto cotton fabric.When the amount of DMHPA reached to 30 wt %,the fiber weight gain was 24.7%,the LOI value reached to 31.1%.The damage length is only 80 mm after VFT and the carbon residue remains intact with bubbles on the surface.By analyzing the results of TG,it is found that the Tmax was advanced,the Rmax decreased from 1.81 to 1.63%/°C,and the carbon residue at 800 ° C increased from 8.9% to 38.0%.CCT result showed that the HRR and THR values were lower than control sample after treating with DMHPA,and treated sample had good ability to reduce the EHC and promote char formation.In addition,it was found that whiteness value of the fabric decreases slightly after treating with DMHPA.To improve the washability after treating,BTCA was added to solution.Through single-factor experiment,the effects of concentration of DMHPA,solution pH,concentration of BTCA,baking time and baking temperature were explored.The experiment proved that the value of LOI can reach target when the concentration of DMHPA was 30 wt %,the pH of solution was 2.5,the concentration of BTCA was 7 wt %,baking temperature was 180 ° C,baking time was 3 min.The surface morphology and chemical composition,the flammability and thermal degradation were characterized by SEM,FTIR,EDS,LOI,VFT,TG and CCT.All the results showed that BTCA connected DMHPA with cotton fabric.Under the best condition,the cotton fabric had a weight gain of 22.3%,the whiteness value dropped to 33.8,the LOI value reached to 30.5%,and the limit oxygen index dropped to 25.1% after 15 washing cycles.After VFT,the fabric damaged 80 mm.Carbon residue under nitrogen conditions increased by 30.5% to 46.4%,and the Rmax decreased by 72.6%.HRR and THR values were lower than those of control sample,and the EHC was significantly reduced.It proved that DMHPA/BTCA finishing system has good performance on flame retardant and washability.